Prolapsed Hemorrhoid?

I have had a problem with hemorrhoids before, but it has been a couple of years since my last one.

Yesturday I had a hard bowel movement, but I had the same kind for the past few days. I didn't notice anything until after I came in from shoveling snow. I went to shovel right after I used the bathroom. Could that have caused the hemorrhoid to appear?

I went to work and was walking around a lot. When I got home there were marks on my underwear. Could the walking around have aggravated the hemorrhoid? Its weird because I had a bowel movement and it didn't seem to be effected.

I am uncomfortable walking and moving my lower half. As long as I am sitting I am fine. When I woke up this morning the hemorrhoid was gone, but I could feel something. I thought I needed to use the bathroom, but as soon as I sat down the hemorrhoid was back.